10 Do’s and Don’ts of RRFBs: Your Ultimate Guide

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Below you will find the top 10 “do’s and don’ts” of using Rectangular Rapid Flashing Beacons, based on what we see working with municipalities every day on RRFB applications.

If you have a location where RRFB solutions are being considered please reach out! We would love to review your plans and ideas. Be sure to refer to the MUTCD Interim Approval 21 – Rectangular Rapid-Flashing Beacons at Crosswalks for the official ruling on the use of RRFBs.

Below is a comprehensive list of RRFB best practices:

1. Use RRFBs only at uncontrolled marked crosswalks

RRFBs are only to be used at crosswalks with pavement markings and signs where vehicles don’t have a stop control. The most common application is where the minor legs have stop signs and the major legs are through lanes. RRFBs can also be used at mid-block locations.

2. Install the RRFB on pedestrian, school, or trail signs, along with down arrow signs

RRFBs must be mounted below the W11-2 Pedestrian, S1-1 School, or W11-15 Trail crossing sign, and above the W16-7P down arrow sign. In Canada the RRFB lightbar is typically mounted above the RA-5 Pedestrian sign, and there is no down arrow.

3. Have RRFBs on both the left and right sides of the crosswalk

For a typical two-way roadway there is a pole on each side of the crosswalk, each with two RRFB lightbars mounted back-to-back. Placing RRFBs on both the left and right side frames the crosswalk and is therefore considered safe for pedestrians as it is more visible to drivers.

4. Signs must also be on both the left and right sides of the crosswalk

The MUTCD requires that pedestrian, school, or trail sign be installed on both the left and right sides of the crosswalk. The signs are typically mounted back-to-back like the lightbars are. This is different from using merely static signs at a crosswalk, where there is typically only a single sign facing oncoming traffic on the right side.

Incorrect Placement 🆇

This location is missing the signs that need to be on the left and right hand side along with the RRFB lightbars. In addition, the lightbar should be mounted between the School sign and the down-arrow sign.

Correct Placement ✅

This location has the correct RRFB lightbar and sign placement. Signs and lightbars are on both the left and right sides of the crosswalk for each approach.

5. Where there is a median, the left RRFB unit goes on the island

The set-up with a median island typically has single-sided light bars on the sides, and the median will have either:

a. one pole with dual back-to-back light bars, or
b. two poles with single sided light bars.

This provides the left and right ‘framing’ and, with the left unit in the middle of the roadway, it is very effective.

See the diagram on our resources page for a median island example of RRFB placement.

6. Where there are parallel crosswalks, a set of one-sided RRFBs should be placed on each crosswalk for maximum safety

Parallel crosswalks are important for serving pedestrians and cyclists who may be crossing a through road from both approaches. Single-sided RRFBs are used in each corner and when any button is pressed all four systems flash.

The diagram below is from the National Committee on Uniform Traffic Control Devices (NCUTCD) recommended changes to Chapter 4L (Rectangular Rapid Flash Beacons) of the proposed draft of the 11th Edition of the MUTCD.

7. RRFBs can also go on overhead mast-arms – instead of just being post-mounted

If an overhead mast-arm is present over a pedestrian crosswalk, a minimum of one RRFB in each direction overhead is required. Typically, there are two RRFBs mounted overhead in each direction – and additional RRFBs can be post mounted as well.

8. Additional RRFBs can be mounted in advance of the units at the crosswalk

RRFBs can be installed in advance of the crosswalk with the pedestrian/school/trail sign along with the Ahead or Distance plaque. Advanced RRFBs are supplemental to and not a replacement for the RRFBs at the crosswalk.

9. Rapid flashing beacons must only flash when activated by a pedestrian

RRFBs are to remain in the off state until activated by a pedestrian, and once activated are to flash for a predetermined time (typically 20-30 seconds). The flash duration is to be based on the same procedures for the timing of pedestrian clearance times for pedestrian signals.

10. The RRFB indications on both sides of the crosswalk must all flash immediately, with no delay, and all turn off together

RRFBs must all start flashing immediately when the button is pressed, with no delay.  If the button is pressed again during the flash sequence the flash time resets.

 

We hope that you have learned some valuable information on RRFB implementation and best practices in this post. If you are looking to increase pedestrian safety in your city please feel free to reach out to us. Together we can walk through your idea and find the perfect options for your project.

 

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Crosswalk with two Availed RRFB poles on a sunny day. A castle-like house stands majestically in the background.

Specifying RRFBs – The Essentials

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This article provides the essential Performance Requirements to include when specifying Rectangular Rapid Flashing Beacons (RRFBs).

Here at Availed Technologies, we work with municipalities and engineering firms across North America everyday who are in the process of specifying RRFBs. We focus on the following three points: Array to Load Ratio, Autonomy, and Shading.

Before we get into the performance requirements it should be noted that the operational requirements of an RRFB are important to specify and these are clearly defined in the MUTCD IA-21. One other point that is discussed at the end of this article is the option to use standard sign posts for RRFBs.

#1: RRFBs and Array to Load Ratio

The Array to Load Ratio is the power coming into the system divided by the power consumed by the system. It is the single most important metric to pay attention to when specifying Solar RRFBs. The ALR Ratio must be greater than 1:1, and a minimum of 1.2:1 is recommended. Regardless of the size of the solar panel or size of the battery, a system with an ALR of less than one means there is a power deficit and the system will run out of power eventually.

For Solar RRFBs, the ALR must be calculated using worst case conditions to ensure reliable year-round operation. This is typically in December when the solar energy available is at a minimum. The Solar insolation for a particular location is available through a comprehensive database from NREL that is based on historical information which accounts for prevailing weather conditions and latitude.

Factoring in the site-specific solar data, the daily power generated by the RRFB is determined by how the device converts the available solar energy into electrical energy that runs the system and is stored in the battery. This calculation is manufacturer-specific and varies significantly from one brand to another.

Power Consumed By RRFBs

The power consumed by the RRFB is also very manufacturer-specific and will vary even more from brand to brand than the power generation side of the equation. Power is consumed by the RRFB lightbars when they flash and also by the wireless connection between the systems which manages the activation of all systems at the crosswalk, so that when any one push button is pressed all the RRFBs start flashing immediately and stop flashing at the same time.

The wireless connection must always be ‘on’ and therefore this function is a significant portion of the power consumed. Advances in both LED and wireless technology have enabled dramatic improvements in power efficiency, the result of which is the ability to achieve a high ALR with a compact and lightweight system.

#2: RRFBs and Autonomy

The autonomy of an RRFB is defined as the number of days it can operate without any charging. It is a function of the daily power consumption and the battery capacity of the system. In an actual installation autonomy is hypothetical because the system will charge in the day even during cloudy conditions. Cold temperatures will decrease the battery capacity and this should be factored into an autonomy calculation.

Autonomy should never be the sole metric used in specifying a solar RRFB because it does not take into account the ‘power in’ of the system. Nevertheless, it is an important consideration as energy storage is essential for the system to function during nighttime and low light conditions. An autonomy of 5-10 days is recommended.

#3: RRFBs and Shading

Shading from trees and buildings is site specific and is often overlooked. At Availed Technologies, we can review the location with google street view and we will incorporate this information when producing the solar performance report.

Key takeaways:

  • Always use ALR and Autonomy when specifying RRFBs
  • Use a solar performance report that factors in site specific shading to ensure system reliability
  • Never specify the solar panel size or battery capacity alone as these metrics do not factor in the power generation and power consumption of the system.

For further information on ALR, Autonomy, and RRFB efficiency see the article The Power of Solar RRFB Systems.

A final consideration when specifying RRFBs is the pole type. A positive benefit of an efficient system is that the product is compact and lightweight which makes it feasible to use standard sign posts. Using 2” Telespar square perforated tubing or standard 2” round sign posts will significantly reduce the installed cost of the system and will simplify the installation process. Standard sign posts can also be helpful for placement of RRFBs in locations where space is limited.

One feature worth mentioning regarding the Availed AV-400 RRFB is that it comes with a Universal mounting system that is compatible with all pole types, from the traditional 4 ½” diameter pedestal poles to 2” square and round posts, and everything in between.

Have any further questions about the essentials of RRFBs? Reach out to our team today!

Guidelines and Warrant Processes for Rectangular Rapid Flashing Beacons

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If you are looking for in-depth info on the guidelines and warrant process for Rectangular Rapid Flashing Beacons, then you’re in the right place.

Here at Availed Technologies, we pride ourselves on being specialists with Solar RRFBs. In today’s article, we explore the guidelines, warrant system, and design process for when and where to use RRFBs at uncontrolled marked crosswalks. Both FHWA and TAC have developed design criteria tools to assist traffic professionals in determining which treatment or treatments should be used for a given crosswalk.

Let’s dive in:

The FHWA Field Guide for Selecting Countermeasures at Uncontrolled Pedestrian Crossing Locations

Let’s look first at the FHWA Field Guide for Selecting Countermeasures at Uncontrolled Pedestrian Crossing Locations.

The first step in the guide is to collect an inventory of the roadway conditions, namely the speed limit, total vehicles per day, travel lane configuration, and approximate total pedestrians per hour (PPH) crossing the roadway.  Other pedestrian safety issues are to be recorded such as noted pedestrian conflicts, excessive vehicle speed, inadequate conspicuity and visibility, drivers not yielding, and insufficient separation between pedestrians and traffic.

The roadway conditions inventory is then used with Table 1 to determine which of the following Pedestrian Crash Countermeasures should be considered for the location.  The Table has rows for the Roadway Configuration (number of lanes, median islands) and columns for the posted speed limit and AADT (Annual Average Daily Traffic).

Pedestrian Crash Countermeasures

A subset of these guidelines involves pedestrian crash countermeasures. These are listed as:

  • High-visibility crosswalk markings, parking restrictions on crosswalk approach, adequate nighttime lighting levels, and crossing warning signs
  • Raised crosswalk
  • Advance Yield Here To (Stop Here For) Pedestrians sign and yield (stop) line
  • In-Street Pedestrian Crossing sign
  • Curb extension
  • Pedestrian refuge island
  • Rectangular Rapid-Flashing Beacon (RRFB, which hold particular importance due to their effectiveness)
  • Road Diet
  • Pedestrian Hybrid Beacon (PHB)

Now that we’ve covered them, let’s turn our overview over to the Transportation Association of Canada (TAC) Pedestrian Crossing Control Guide.

TAC Pedestrian Crossing Control Guide

Similar to the FHWA Pedestrian Crash Countermeasures, the TAC Pedestrian Crossing Control Guide includes a Treatment Selection Matrix where vehicle volume, speed limit, and total number of lanes are the primary variables used to determine which of the following crossing treatment options should be considered.

These crosswalk treatment options encompass the following tools:

  • Crosswalk with side mounted signs (GM)
  • Enhanced crosswalk with side-mounted signs (GM+) which includes advance yield lines, curb extensions, raised pedestrian refuge, and in-street signs
  • Rectangular Rapid Flashing Beacon
  • Overhead Flashing Beacon
  • Traffic Signal

In our opinion, the current third version of the TAC Pedestrian Crossing Control Guide from 2018 is somewhat outdated, in that RRFBs are now commonly used in overhead applications and should be considered instead of overhead flashing beacons. RRFBs have been demonstrated to be significantly more effective than traditional round flashing beacons.

The TAC Pedestrian Crossing Control Guide also includes a flow chart intended to be used as a preliminary decision support tool.  The tool includes Average Hourly Pedestrian Volume as a criteria, and includes a weighting system where pedestrian volume is converted to Equivalent Adult Units (EAU) to account for pedestrian age and physical ability or at-risk pedestrians.

Key Takeaways Regarding Guidelines and Warrant Processes for Uncontrolled Marked Crosswalks

According to the FHWA Countermeasure Tech Sheet, the average cost of an RRFB system is USD $22,250, with a range of $4,500 to $52,000 each.

Systems like the Availed AV-400 RRFB that are highly efficient have a much smaller form factor than previous technology, and the smaller size greatly reduces the installed cost in the following ways:

  • Has lower material costs compared to larger, less efficient systems
  • Is lightweight and easy to handle, thereby significantly reducing installation time
  • Can be easily pre-installed on the pole prior to being on site
  • Can be readily mounted onto existing sign posts. This is perhaps the greatest opportunity to minimize the installed cost, as the existing sign post footings can often be used which eliminates any expensive work involving the pole foundations. Regular sign posts are also significantly less costly than the larger poles that are necessary to support larger, less efficient solar RRFBs.

By utilizing existing sign posts, an agency can install three-to-five RRFB systems for the USD $22,250 average cost noted in the 2018 FHWA Tech Sheet.

Another factor that is implicit in the crosswalk treatment decision process is the concern with the overuse of crosswalk treatments.  The argument is that crosswalks and sign treatments should be used discriminately so that the effectiveness of these treatments is not deteriorated by overuse.  The concern for overuse of traffic signs is fundamental in the FHWA MUTCD, as noted in Section 2A.04 Excessive Use of Signs.

We here at Availed Technologies argue that the ‘Active’ nature of an RRFB makes the device largely immune to the risk of overuse.  An RRFB system that is not flashing will not contribute to any deterioration of effectiveness in the same way that prolific use of enhanced signs or pavement marking  will.  To this end, a requirement for a minimum number of pedestrians per hour arguably does not apply to RRFBs in the context of overuse.

Many agencies have developed their own decision process for prioritizing and selecting improvements for uncontrolled marked crosswalks. In many places, RRFBs have become a key tool that is used, owing to their high effectiveness, relatively low cost, and advantages of being an Active device that is not prone to overuse in the same way as passive treatments are.

Considering using RRFBs in an upcoming project?

Our expert team is here to answer all your questions. Contact us today.